Because it is a leading contributor to racial and ethnic disparities in infant mortality, the Centers for Disease Control and Prevention has identified preterm birth as a vital subject for public health research. While the causes of preterm birth and preterm birth disparities are not well understood, a growing body of literature implicates neighborhood social and material environments as determinants of poor birth outcomes. Residential segregation organizes racial and ethnic groups into different neighborhoods, and as such it may contribute to preterm birth disparities by influencing the distribution of risk factors and resources across population groups. Thus, building a nation of Healthy People in Healthy Places may depend on addressing residential segregation as a social determinant of health in minority communities. Previous research has documented detrimental social, economic, and health effects of residential segregation on the US black population. Some theoretical literature and a few epidemiologic studies have suggested that neighborhood-level racial/ethnic homogeneity resulting from segregation may be beneficial for certain health outcomes, however. Segregation may, in fact, have both positive and negative effects on health, the balance of which may differ across ethnic groups and contexts; for example, positive birth outcomes among Hispanics are often attributed to beneficial health behaviors and social support that may be promoted in Hispanic neighborhoods. Thus, appropriately addressing residential segregation as a social determinant of preterm birth requires an understanding of the potentially complex relationship between segregation and health. Because most studies of segregation and health have included only US-born non-Hispanic black and white populations, however, this complexity remains largely unexplored. Moreover, previous studies have used aspatial measures of segregation that ignore potentially important spatial relationships between neighborhoods. The proposed study will use a spatial measure of segregation and New York City birth records (1995-2003) linked to 2000 Census data in order to (1) assess the effects of segregation, defined as own-ethnic-group density in the residential area, on preterm birth risk in 14 groups including US- and foreign-born whites, blacks, Hispanics, and Asians; (2) examine whether preterm birth risk among black women residing in non-black neighborhoods is affected by the specific ethnic groups that are present; and (3) among foreign-born black women, explore the extent to which preterm birth risk is influenced by the density of individuals in a woman's neighborhood who share her region-of-origin ("cultural") group. [unreadable] [unreadable] [unreadable]